Portulacaria is a small genus of succulent plants in the family Didiereaceae (order Caryophyllales), placed in its own subfamily Portulacarioideae. The genus is indigenous to southern Africa, where its members grow as shrubs or small trees with fleshy, water-storing leaves adapted to arid and semi-arid conditions.
The genus was formerly classified in the family Portulacaceae, but molecular studies established its position within Didiereaceae. A significant taxonomic revision absorbed the closely related genus Ceraria into Portulacaria after phylogenetic analyses showed conclusively that Ceraria species were nested within Portulacaria; all former Ceraria species have been renamed accordingly and the genus now comprises around seven accepted species.
The most widely known member is Portulacaria afra, commonly called elephant bush or spekboom. It is notable for its dual carbon-fixation capability: it normally uses C3 photosynthesis but can switch to CAM photosynthesis under drought stress, an unusual physiological flexibility. P. afra is eaten as a leafy vegetable by local peoples of southern Africa and is also cultivated globally as a garden and houseplant. Its superficial resemblance to certain Crassulaceae — many of which are toxic — can lead to dangerous misidentification.
Distribution
Portulacaria is indigenous to southern Africa. The genus occupies arid and semi-arid habitats across the region, with Portulacaria afra (spekboom) forming extensive thicket communities in the Eastern Cape and other parts of South Africa.
Taxonomy Notes
Portulacaria was long placed in Portulacaceae but molecular phylogenetics confirmed its position in Didiereaceae, subfamily Portulacarioideae. A subsequent revision absorbed the entire genus Ceraria into Portulacaria once phylogenetic analyses demonstrated that Ceraria was nested within it; all former Ceraria species have been recombined under Portulacaria.
Cultural Uses
The leaves of Portulacaria afra are consumed as a leafy vegetable by local peoples of southern Africa. The species is also widely cultivated as a garden and houseplant internationally. Caution is warranted, as its appearance is superficially similar to some members of Crassulaceae, many of which are toxic; the two groups are sometimes confused by people unfamiliar with the differences.
